CBSE Class 12 · 2023 · Chemical KineticsShort Answer

(a) For the reaction

2 N_{2} O_{5} (g) \to 4 N O_{2} (g) + O_{2} (g)

at 318 K, calculate the rate of reaction if the rate of disappearance of N

_{2}

_{5}

(g) is

1.4 \times 1 0^{- 3}

M s

^{- 1}

.
(b) For a first order reaction, derive the relationship t

_{99%}

= 2 t

_{90%}

Answer: (a) Rate = 7 × 10⁻⁴ M s⁻¹. (b) t₉₉ = (2.303/k)·2, t₉₀ = (2.303/k)·1 ⟹ t₉₉ = 2t₉₀.

Solution

(a)

Rate = - \frac{1}{2} \frac{d [ N _{2} O _{5} ]}{d t} = \frac{1}{2} \times 1.4 \times 1 0^{- 3}

Rate = 7 \times 1 0^{- 4} M s^{- 1}

(b) First order:

t = \frac{2.303}{k} lo g \frac{[ R ] _{0}}{[ R ]}

t_{99%} = \frac{2.303}{k} lo g \frac{100}{1} = \frac{2.303}{k} \times 2

t_{90%} = \frac{2.303}{k} lo g \frac{100}{10} = \frac{2.303}{k} \times 1

t_{99%} = 2 t_{90%}

CBSE Class 12 Board · 2023 · Subjective